1. Field of the Invention
The present invention relates to a technology suitable for funduscopic image processing for displaying a funduscopic image output from a fundus camera used in departments of ophthalmology and internal medicine.
2. Related Background Art
The present invention relates to a funduscopic image processing unit for correctly displaying a funduscopic image output from a fundus camera used in departments of ophthalmology and internal medicine.
FIG. 7 shows a periphery of a photographic camera of a fundus camera having means for photographing an aperture mask. Right in front of an imaging face of the photographic camera 1 for static images, an aperture mask plate 3 having a circular opening 2 provided in the center and a shading part around it, is arranged as shown in FIG. 8.
A funduscopic image is caught in the center of a photographic light flux from a photographic optical system of a fundus camera, but a flare is mixed with the funduscopic image in the perimeter, and undesired reflection and the like are mixed with the funduscopic image outside the perimeter, so that the opening 2 of an effective region for diagnosis, is preferably clarified by an aperture mask plate 3.
In this case, the aperture mask plate 3 has to be arranged in such a vicinity of the imaging face of a photographic camera 1 as not to blur a mask border. However, if various filters and a changeover mirror 4 are arranged right in front of an imaging face, it is rather difficult to further install the aperture mask plate 3 there.
Particularly, in the case of using a three-plate camera having three image sensors behind a color-splitting prism such as a 3P prism, the camera has to optically reimage an aperture mask plate 3 and a funduscopic image in order to photograph an image of the aperture mask plate 3, as a result, needs to make an optical path longer, an optical system complicated and the number of mechanisms increased, and causes problems of an increase of the cost and the like.
In recent years, a fundus camera is proposed which in order to reduce the cost, miniaturizes the unit and reduces the weight, simplifies the optical system and mechanisms, eliminates the above described aperture mask plate 3, and makes the whole image of a photographically effective area of a photographic optical system produced on the imaging face. By such means, the photographic system eliminates an optical system for reimaging, thereby miniaturizes a fundus camera itself, and reduces the cost.
As described above, there are various types in funduscopic images photographed by a conventional fundus camera, as shown in FIGS. 9A to 9D. FIGS. 9A and 9B show funduscopic images with the use of an aperture mask plate 3, and FIGS. 9C and 9D show funduscopic images without the use of an aperture mask plate 3. FIG. 9A shows a funduscopic image of an ocular fundus, which shows an orbicular funduscopic image Er′, is photographed at the same view angles both in vertical and horizontal directions, and catches an aperture mask image M in the perimeter. In FIG. 9B, the photographic optical system effectively arranges both of an effective optical path and an imaging face therein, and catches a funduscopic image Er′ as an oval and oblong shape in a horizontal direction and an aperture mask image M around it.
In FIG. 9C, the photographic optical system arranges all imaging faces inside a photographing light flux, and catches a funduscopic image Er′ on the whole image plane. FIG. 9D shows a funduscopic image Er′ which schematically shows a flare, and in which flares F1, F2 and F3 are sequentially caught outside an effective funduscopic image Er′. The flare F1 is an area in which a funduscopic image is photographed together with a flare. In the flare F2, a funduscopic image, an image in a fundus camera and a flare are shown. In the flare F3, a blurred image in a fundus camera is darkly shown. In Japanese Patent Application Laid-Open No. H09-206278, it is disclosed to electrically and electronically add an aperture mask image to a funduscopic image photographed by the above fundus camera.
There is no problem in using a fundus camera integrated with means for mask processing, as described above. However, in the case of using a fundus camera in fundus photography for health examination, diabetic retinopathy and a diagnosis of glaucoma, a diagnosis based on a photographed funduscopic image is generally carried out in a different place from that for the fundus photography. Particularly, a small, light weight and inexpensive product is demanded for the fundus camera, which causes a problem that a fundus camera hardly integrates means for mask processing in its inside.
In addition, because various old and new fundus cameras described above are installed in a hospital or a physical examination organization which carries out fundus photography for such examinations, if a funduscopic image as shown in FIG. 9D is mixed, it may cause a wrong diagnosis because of the image which does not define an effective range of an ocular fundus. Furthermore, because it is hard to observe and interpret the image having no boundary, such images cause the problem of imposing a heavier load of easily being tired onto an image diagnostician.